The present invention relates to a mounting construction of a lightning arrester for a neutral point of a transformer, and more particularly to a mounting construction of a tank-type lightning arrester for a neutral point of a transformer.
As shown in FIG. 5, a conventional power transformer, having a capacity of 6 KV to 154 KV, is operated in a resistance grounded system, and a lightning arrester 3 is connected to a neutral point 2a of transformer windings 2 of the power transformer 1 so as to protect the transformer 1 from an overvoltage.
One example of such conventional technique is an insulator-type lightning arrester, and as shown in FIG. 6, the lightning arrester 7 is mounted on an upper portion of a transformer 4 or a mounting base, and a neutral point of the transformer is connected to the lightning arrester 7 via a bushing 6. Another example is a tank-type lightning arrester, and as shown in FIG. 7, a neutral point 2a of a transformer 2 is connected to a tank-type lightning arrester 12 via an oil-gas bushing 10, projecting from a transformer tank 9, and a disconnecting switch 11. The tank-type lightning arrester 12 is mounted on a mounting base 13 mounted on the earth.
Japanese Patent Examined Publication No. 6-30286 discloses an example in which a lightning arrester is arranged parallel to a neutral grounding resistor within a tank.
However, in the mounting construction of the conventional insulator-type lightning arrester shown in FIG. 6, the lightning arrester 7 is inferior in earthquake resistance and anti-pollution characteristics. In the mounting construction of the tank-type lightning arrester 12 shown in FIG. 7, the drawback of the insulator-type lightning arrester has been overcome, and there has been achieved an advantage that this tank-type lightning arrester can be easily disconnected from the transformer 2 when effecting a voltage-withstanding test of the transformer. However, since the oil-gas bushing 10 of which creeping distance is long and which requires a long extension distance for connection from a transformer tank 9 is provided for connecting the transformer 2 to the tank-type lightning arrester 12, the distance L1 between the transformer 2 and the tank-type lightning arrester 12 is long, and a large installation area is required for installing the tank-type lightning arrester 12, and this is not economical.
In the conventional construction disclosed in Japanese Patent Examined Publication No. 6-30286, any mounting bracket member is not formed on a side surface of the tank, and therefore a large installation area is required for installing the lightning arrester.